1. Field of the Invention
This invention relates to reduction of carbonyl values in compositions containing carboxylic acids, derivatives of carboxylic acids or both.
2. Description of Related Art
Carboxylic acid and carboxylic acid derivative containing compositions have a multitude of uses as intermediates in the production of materials and as final products. Various processes have been used to produce carboxylic acids and derivatives thereof. These products are then stored or subject to further processing. The processing and storage of these products can result in degradation of the carboxylic acids and contamination of the products. For example, production of azelaic acid or pelargonic acids by ozonolysis of oleic acid is known to lead to a mixture of oxidation products containing carboxylic acids and carbonyl-containing species such as aldehydes and ketones. The presence of aldehydes and ketones may be considered undesirable since they may impart discoloration, odors and tastes to such products. Indeed, processing and storage of fatty acids and derivatives of fatty acids may lead to aldehyde and ketone degradation products resulting from oxidation.
The combined concentration of aldehydes and ketones is known interchangeably as the carbonyl content or carbonyl value. In the present context, the carbonyl value is also a measure of oxidation and may be expressed as milligrams of carbonyl functionality per gram of sample. Carbonyl value is abbreviated COV and may also be expressed in parts per million.
Since aldehydes, ketones and oxo-carboxylic acid derivatives thereof may be considered undesirable contaminants in compositions containing carboxylic acids and derivatives thereof, certain processes have been developed to lower the COV. Typically, keto-acids and aldo-acids are contaminants which are difficult to remove from the carboxylic acid end products, especially on industrial scales. One removal process involves reaction of ketones and aldehydes with oxygen in the presence of a metal ion catalyst such as cobalt and manganese. Unfortunately, treatment with oxygen may result in degradation of the product and toxic manganese or cobalt waste products. The presence of manganese or cobalt in waste streams can present environmental problems.
Consequently, there exists a need for methods of lowering COV, but which eliminates the need for manganese compounds and oxygen for the removal of aldehydes and ketones.